Conventionally, such a printing apparatus has been known widely that forms an image on a transfer medium such as an image carrying body or a printing medium such as a card and sheet. For example, this type of printing apparatus uses an indirect printing scheme for forming an image (mirror image) on a transfer medium using an ink ribbon, and next transferring the image formed on the transfer medium to a printing medium, or a direct printing scheme for forming an image directly on a printing medium using an ink ribbon.
In such a printing apparatus, generally, color printing for generating a color image is performed by superimposing respective printing images with a plurality of color inks. In other words, color printing is performed by superimposing a printing image for each of a plurality of color inks (for example, inks of YMC) on a medium (transfer medium in the indirect printing scheme, printing medium in the direct printing scheme), according to input printing data or printing data (for example, printing data for each of Y (Yellow), M (Magenta) and C (Cyan)) obtained by converting input image data.
In color printing, when printing positions of respective printing images of color inks on the medium are shifted, since the color image printed on the medium is blurred, the printing quality (image quality) degrades. In addition, the phenomenon that the printing position of the printing image of each color is shifted is generally called the “color shift”. Therefore, techniques are disclosed to correct the printing position of the printing image of each color. For example, proposed are techniques for printing a concentration correction pattern and color shift correction pattern on an intermediate transfer belt to reduce the correction time (see Patent Document 1) and techniques for using an unused region that is not used in image printing inside an image formation-capable region to make a register adjustment (see Patent Document 2).